1. Field of the Invention
The present invention relates to computer systems which have mouse and/or keyboard type of input devices coupled thereto. More particularly, the present invention relates to apparatus and methods wherein the device driver associated with the attached mouse or keyboard in the form of hardware, or as a part of a personal computer operating system, is capable of supporting the keyboard, or pointing device, which is disconnected or experiences a temporary loss of power. Still further, the present invention relates to personal computer systems wherein the pointing device driver can recover from a low power state in which the pointing device has not lost all power, but has become disabled which is a default state.
As used herein, "hot plugging" means the temporary disruption of interfacing connections, or power, between a computer processor and keyboard, mouse, or similar input devices, with subsequent resumption of the physical or power connections while the computer processor is active. Support for a hot plug in a pointing device as defined herein is the ability for the operating system, in general, and the pointing device driver, in particular, to recover from the disruption in a manner substantially transparent to the user, or at least not requiring user intervention. Note that an apparent power intervention could result from a spurious source even in the computer itself, and not from an actual power loss or disconnection of the peripheral device.
2. Description of the Prior Art
Personal computers in general, and notebook sized computers in particular, have become extremely popular in recent years. The notebook computers often rely upon battery power for operation. Thus, they are sometimes designed to monitor their input and enter a reduced power state upon detection of lack of use over a predetermined period of time. This is intended to extend the life of the battery. The computer resumes normal operation upon actuation of any key by the user.
Note that keyboards and pointing devices, such as mice, are considered synonymous for purposes of this patent application. Unfortunately, a power down and power up sequence, along the lines of that described above, frequently causes an attached mouse to enter a default state requiring re-initialization by the operating system. In the default state, the pointing device is in a ready mode waiting for commands on what state it should enter.
Personal computers, including the notebook type, typically have a pointing device plugged into the system mouse port. Prior art computer operating systems were unable to recognize the pointing device when the system resumed its full power state due to internal workings of the pointing device hardware. In its default state, pointing devices for the computer system, such as the IBM Personal System/2 (PS/2), do not report events. The only way to return the device to usefulness is for the pointing device driver to program it to a useful state. Unfortunately, this requires restarting, or re-booting, of the computer operating system with its attendant disadvantages.
Note that PS/2 and MicroChannel are trademarks of the International Business Machines Corporation.